Add initial support for x: my_enum_type = /*value*/;, closes #670

Author: hsutter

include/cpp2util.h

@@ -279,6 +279,18 @@ using __schar   = signed char;      // normally use i8 instead
 using __uchar   = unsigned char;    // normally use u8 instead
 
 
+//-----------------------------------------------------------------------
+//
+//  General helpers
+//
+//-----------------------------------------------------------------------
+//
+
+auto max(auto... values) {
+    return std::max( { values... } );
+}
+
+
 //-----------------------------------------------------------------------
 //
 //  String: A helper workaround for passing a string literal as a
@@ -1797,8 +1809,14 @@ inline constexpr auto as_() -> decltype(auto)
 
 using cpp2::cpp2_new;
 
-// Workaround GCC 10 not supporting requires in forward declarations in some cases.
-// See commit 5a0d77f8e297902c0b9712c5aafb6208cfa4c139.
+
+//  Stabilize line numbers for "compatibility" static assertions that we know
+//  will fire for some compilers, to keep regression test outputs cleaner
+#line 9999
+
+//  GCC 10 doesn't support 'requires' in forward declarations in some cases
+//  Workaround: Disable the requires clause where that gets reasonable behavior
+//  Diagnostic: static_assert the other cases that can't be worked around
 #if !defined(__clang__) && defined(__GNUC__) && __GNUC__ == 10
     #define CPP2_REQUIRES(...) /* empty */
     #define CPP2_REQUIRES_(...) static_assert(false, "GCC 11 or higher is required to support variables and type-scope functions that have a 'requires' clause. This includes a type-scope 'forward' parameter of non-wildcard type, such as 'func: (this, forward s: std::string)', which relies on being able to add a 'requires' clause - in that case, use 'forward s: _' instead if you need the result to compile with GCC 10.")

regression-tests/pure2-enum.cpp2

@@ -1,4 +1,5 @@
 
+
 skat_game: @enum type = {
     diamonds := 9;
     hearts;  // 10
@@ -24,12 +25,15 @@ file_attributes: @flag_enum type = {
 main: () = {
     // x : skat_game = 9;               // error, can't construct skat_game from integer
 
-    x := skat_game::clubs;
+    x: skat_game = skat_game::clubs;
+    x2 := skat_game::diamonds;
+    x2 = x;
 
     // if x == 9 { }                    // error, can't compare skat_game and integer
     // if x == rgb::red { }             // error, can't compare skat_game and rgb color
 
     std::cout << "x.to_string() is (x.to_string())$\n";
+    std::cout << "x2.to_string() is (x2.to_string())$\n";
     std::cout << "using << prints " << x << "\n";
 
     std::cout << "with if else: ";
@@ -62,7 +66,7 @@ main: () = {
 
     x = skat_game::diamonds;        // ok, can assign one skat_game from another
 
-    f := file_attributes::cached_and_current;
+    f: file_attributes = file_attributes::cached_and_current;
     f &= file_attributes::cached  | file_attributes::obsolete;
 
     f2 := file_attributes::cached;

regression-tests/test-results/clang-12/pure2-enum.cpp.execution

@@ -1,4 +1,5 @@
 x.to_string() is clubs
+x2.to_string() is clubs
 using << prints clubs
 with if else: clubs
 with inspect: clubs

regression-tests/test-results/gcc-10/pure2-bugfix-for-requires-clause-in-forward-declaration.cpp.output

@@ -3,30 +3,26 @@ pure2-bugfix-for-requires-clause-in-forward-declaration.cpp:16:36: error: expect
       |                                    ^
       |                                     ;
 In file included from pure2-bugfix-for-requires-clause-in-forward-declaration.cpp:7:
-../../../include/cpp2util.h:1804:47: error: static assertion failed: GCC 11 or higher is required to support variables and type-scope functions that have a 'requires' clause. This includes a type-scope 'forward' parameter of non-wildcard type, such as 'func: (this, forward s: std::string)', which relies on being able to add a 'requires' clause - in that case, use 'forward s: _' instead if you need the result to compile with GCC 10.
- 1804 |     #define CPP2_REQUIRES_(...) static_assert(false, "GCC 11 or higher is required to support variables and type-scope functions that have a 'requires' clause. This includes a type-scope 'forward' parameter of non-wildcard type, such as 'func: (this, forward s: std::string)', which relies on being able to add a 'requires' clause - in that case, use 'forward s: _' instead if you need the result to compile with GCC 10.")
-      |                                               ^~~~~
+../../../include/cpp2util.h:10005:47: error: static assertion failed: GCC 11 or higher is required to support variables and type-scope functions that have a 'requires' clause. This includes a type-scope 'forward' parameter of non-wildcard type, such as 'func: (this, forward s: std::string)', which relies on being able to add a 'requires' clause - in that case, use 'forward s: _' instead if you need the result to compile with GCC 10.
 pure2-bugfix-for-requires-clause-in-forward-declaration.cpp:17:1: note: in expansion of macro ‘CPP2_REQUIRES_’
    17 | CPP2_REQUIRES_ (std::is_same_v<CPP2_TYPEOF(n), std::string>)
       | ^~~~~~~~~~~~~~
 pure2-bugfix-for-requires-clause-in-forward-declaration.cpp2:3:46: error: expected ‘;’ at end of member declaration
 In file included from pure2-bugfix-for-requires-clause-in-forward-declaration.cpp:7:
-../../../include/cpp2util.h:1804:47: error: static assertion failed: GCC 11 or higher is required to support variables and type-scope functions that have a 'requires' clause. This includes a type-scope 'forward' parameter of non-wildcard type, such as 'func: (this, forward s: std::string)', which relies on being able to add a 'requires' clause - in that case, use 'forward s: _' instead if you need the result to compile with GCC 10.
- 1804 |     #define CPP2_REQUIRES_(...) static_assert(false, "GCC 11 or higher is required to support variables and type-scope functions that have a 'requires' clause. This includes a type-scope 'forward' parameter of non-wildcard type, such as 'func: (this, forward s: std::string)', which relies on being able to add a 'requires' clause - in that case, use 'forward s: _' instead if you need the result to compile with GCC 10.")
-      |                                               ^~~~~
+../../../include/cpp2util.h:10005:47: error: static assertion failed: GCC 11 or higher is required to support variables and type-scope functions that have a 'requires' clause. This includes a type-scope 'forward' parameter of non-wildcard type, such as 'func: (this, forward s: std::string)', which relies on being able to add a 'requires' clause - in that case, use 'forward s: _' instead if you need the result to compile with GCC 10.
 pure2-bugfix-for-requires-clause-in-forward-declaration.cpp2:4:1: note: in expansion of macro ‘CPP2_REQUIRES_’
-pure2-bugfix-for-requires-clause-in-forward-declaration.cpp2:3:3: error: no declaration matches ‘element::element(auto:80&&) requires  is_same_v<typename std::remove_cv<typename std::remove_reference<decltype(element::__ct ::n)>::type>::type, std::__cxx11::string>’
+pure2-bugfix-for-requires-clause-in-forward-declaration.cpp2:3:3: error: no declaration matches ‘element::element(auto:81&&) requires  is_same_v<typename std::remove_cv<typename std::remove_reference<decltype(element::__ct ::n)>::type>::type, std::__cxx11::string>’
 pure2-bugfix-for-requires-clause-in-forward-declaration.cpp2:5:11: note: candidates are: ‘element::element(const element&)’
-pure2-bugfix-for-requires-clause-in-forward-declaration.cpp:16:20: note:                 ‘template<class auto:78> element::element(auto:78&&)’
+pure2-bugfix-for-requires-clause-in-forward-declaration.cpp:16:20: note:                 ‘template<class auto:79> element::element(auto:79&&)’
    16 |   public: explicit element(auto&& n)
       |                    ^~~~~~~
 pure2-bugfix-for-requires-clause-in-forward-declaration.cpp:14:7: note: ‘class element’ defined here
    14 | class element {
       |       ^~~~~~~
 pure2-bugfix-for-requires-clause-in-forward-declaration.cpp2:3:3: error: expected unqualified-id before ‘{’ token
-pure2-bugfix-for-requires-clause-in-forward-declaration.cpp2:3:8: error: no declaration matches ‘element& element::operator=(auto:81&&) requires  is_same_v<typename std::remove_cv<typename std::remove_reference<decltype(element::operator=::n)>::type>::type, std::__cxx11::string>’
+pure2-bugfix-for-requires-clause-in-forward-declaration.cpp2:3:8: error: no declaration matches ‘element& element::operator=(auto:82&&) requires  is_same_v<typename std::remove_cv<typename std::remove_reference<decltype(element::operator=::n)>::type>::type, std::__cxx11::string>’
 pure2-bugfix-for-requires-clause-in-forward-declaration.cpp2:6:16: note: candidates are: ‘void element::operator=(const element&)’
-pure2-bugfix-for-requires-clause-in-forward-declaration.cpp2:3:16: note:                 ‘template<class auto:79> element& element::operator=(auto:79&&)’
+pure2-bugfix-for-requires-clause-in-forward-declaration.cpp2:3:16: note:                 ‘template<class auto:80> element& element::operator=(auto:80&&)’
 pure2-bugfix-for-requires-clause-in-forward-declaration.cpp:14:7: note: ‘class element’ defined here
    14 | class element {
       |       ^~~~~~~

regression-tests/test-results/gcc-10/pure2-enum.cpp.execution

@@ -1,4 +1,5 @@
 x.to_string() is clubs
+x2.to_string() is clubs
 using << prints clubs
 with if else: clubs
 with inspect: clubs

regression-tests/test-results/gcc-10/pure2-requires-clauses.cpp.output

@@ -1,5 +1,3 @@
 In file included from pure2-requires-clauses.cpp:7:
-../../../include/cpp2util.h:1804:33: error: expected unqualified-id before ‘static_assert’
- 1804 |     #define CPP2_REQUIRES_(...) static_assert(false, "GCC 11 or higher is required to support variables and type-scope functions that have a 'requires' clause. This includes a type-scope 'forward' parameter of non-wildcard type, such as 'func: (this, forward s: std::string)', which relies on being able to add a 'requires' clause - in that case, use 'forward s: _' instead if you need the result to compile with GCC 10.")
-      |                                 ^~~~~~~~~~~~~
+../../../include/cpp2util.h:10005:33: error: expected unqualified-id before ‘static_assert’
 pure2-requires-clauses.cpp2:19:1: note: in expansion of macro ‘CPP2_REQUIRES_’

regression-tests/test-results/gcc-13/pure2-enum.cpp.execution

@@ -1,4 +1,5 @@
 x.to_string() is clubs
+x2.to_string() is clubs
 using << prints clubs
 with if else: clubs
 with inspect: clubs

regression-tests/test-results/msvc-2022/pure2-enum.cpp.execution

@@ -1,4 +1,5 @@
 x.to_string() is clubs
+x2.to_string() is clubs
 using << prints clubs
 with if else: clubs
 with inspect: clubs